Near-field light generator plate, thermally assisted magnetic head, head gimbal assembly, and hard disk drive

ABSTRACT

A near-field light generator plate  36  of the present invention is arranged to face a medium  10,  and one portion  36   b  and other portion  36   a  in a medium-facing surface S thereof are made of their respective electroconductive materials different from each other. Since the one portion and the other portion in the medium-facing surface are made of the electroconductive materials different from each other, this medium-facing surface is formed by a surface removing step such as polishing or etching from the medium-facing surface side so that a difference between heights of the one portion and the other portion is readily made based on the difference of the materials.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a near-field light generator plate, athermally assisted magnetic head for writing of signals by thermallyassisted magnetic recording, a head gimbal assembly (HGA) with thisthermally assisted magnetic head, and a hard disk drive with this HGA.

2. Related Background Art

As the recording density of the hard disk drive increases, furtherimprovement is demanded in the performance of the thin film magnetichead. In order to increase the recording density, a recording medium ismade of a magnetic material with large K_(U) and the so-called thermallyassisted magnetic recording is proposed as a method of applying heat tothe recording medium right before application of a writing magneticfield to lower the coercivity of the magnetic material, and thenperforming writing.

As examples of such thermally-assisted magnetic head recordingapparatus, Japanese Patent Application Laid-Open No. 2001-255254 andJapanese Patent Application Laid-Open No. 2003-114184 and T. Matsumotoet al., Near-Field Optical Probe with A Beaked Metallic Plate forThermally Assisted Magnetic Recording, pp. 6-7, MORIS2006 WORKSHOPTechnical Digest, Jun. 6-8, 2003 disclose the thermally-assistedmagnetic heads in which an electroconductive near-field light generatorplate of a plate shape is disposed on a medium-facing surface and inwhich light is guided onto the near-field light generator plate from theback side to generate near-field light. Particularly, Japanese PatentApplication Laid-Open No. 2003-114184 and T. Matsumoto et al.,Near-Field Optical Probe with A Beaked Metallic Plate for ThermallyAssisted Magnetic Recording, pp. 6-7, MORIS2006 WORKSHOP TechnicalDigest, Jun. 6-8, 2003 disclose the structure in which a part of thenear-field light generator plate is projected toward the medium, and itis considered that in this structure the near-field light is selectivelyradiated at high intensity from the projected part toward the medium.

SUMMARY OF THE INVENTION

The above-cited Documents, however, failed to disclose the details abouthow to make a desired portion of the near-field light generator plateprojected toward the medium.

An object of the present invention is therefore to provide a near-fieldlight generator plate any desired portion of which can be readilyprojected toward the medium, a thermally assisted magnetic head, an HGAwith this thermally assisted magnetic head, and a hard disk drive withthis HGA.

A near-field light generator plate according to the present invention isa near-field light generator plate which is arranged so that a principalsurface thereof faces a medium, and in which one portion and otherportion in the principal surface are made of respectiveelectroconductive materials different from each other.

According to the present invention, the one portion and the otherportion in the principal surface or the medium-facing surface of thenear-field generator plate are made of their respectiveelectroconductive materials different from each other. Therefore, thismedium-facing surface is formed by a surface removing step such aspolishing or etching from the medium-facing surface side whereby adifference between heights of surfaces of the one portion and the otherportion can be readily formed based on a difference between physicalproperties of the materials. It is thus easy to control degrees ofprojections of the respective portions toward the medium in thenear-field light generator plate, and the near-field light generatorplate is readily obtained in a form where a desired portion in themedium-facing surface is selectively projected toward the medium.

Preferably, each of the electroconductive materials is a metal or analloy of two or more metals selected from a metal group consisting ofPd, Pt, Rh, Ir, Ru, Au, Ag, Cu, and Al. This configuration achieves theeffect that the surface plasmon is effectively induced in the wavelengthregion of visible light to generate the near-field light.

Preferably, the electroconductive material of the one portion has ahigher hardness or a lower etching speed than the electroconductivematerial of the other portion. This makes it easy to make the height ofthe surface of the one portion higher than that of the other portion bya surface removing step such as polishing or etching.

Preferably, the one portion is projected more toward the medium than theother portion. Since electric charge is concentrated particularly in theprojected portion, the near-field light can be selectively radiated fromthis projected portion toward the medium, which increases the recordingdensity.

Preferably, when viewed from a direction normal to the medium-facingsurface, the one portion has a cusp portion, whereby the near-fieldlight is selectively radiated particularly from the tip of the cuspportion of the one portion. In a preferred configuration the one portionhas only one cusp portion.

Preferably, the one portion is made of AuCu and the other portion ismade of Au.

A thermally assisted magnetic head according to the present invention isa thermally assisted magnetic head comprising: a magnetic pole forgenerating a magnetic field, which is exposed in a medium-facingsurface; a waveguide for receiving light from the outside and guidingthe light to the medium-facing surface; and the above-describednear-field light generator plate disposed on a medium-facing surface ofthe waveguide.

Another thermally assisted magnetic head according to the presentinvention is a thermally assisted magnetic head comprising: a magneticpole for generating a magnetic field, which is exposed in amedium-facing surface; a waveguide for receiving light from the outsideand guiding the light to the medium-facing surface; and theabove-described near-field light generator plate disposed on amedium-facing surface of the waveguide; wherein in the medium-facingsurface, the one portion of the near-field light generator plate iscloser to the magnetic pole than the other portion thereof. In thisconfiguration, the one portion from which the near-field light isselectively radiated in the near-field light generator plate, becomescloser to the magnetic pole, so as to shorten a time from heating of themedium with the near-field light to application of a recording magneticfield, whereby recording magnetism can be applied to the medium beforethe temperature of the medium heated with the near-field light decreaseslargely.

A head gimbal assembly according to the present invention is a headgimbal assembly comprising the above-described thermally assistedmagnetic head, and a suspension supporting the thermally assistedmagnetic head.

A hard disk drive according to the present invention comprises theabove-described head gimbal assembly, and a magnetic recording medium.

Since the present invention enables a desired portion of the near-fieldlight generator to be readily projected toward the medium, a spot sizeof the near-field light can be made smaller and high-density recordingcan be readily realized by the thermally assisted magnetic recording.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically showing a configuration of amajor part in an embodiment of a hard disk drive and HGA according tothe present invention.

FIG. 2 is an enlarged perspective view of a part near a distal end ofthe HGA in FIG. 1.

FIG. 3 is a perspective view schematically showing a configuration of athermally assisted magnetic head in FIG. 1.

FIG. 4 is a sectional view perpendicular to a medium-facing surface ofthe thermally assisted magnetic head in FIG. 3.

FIG. 5 is a schematic view from the medium-facing surface of thethermally assisted magnetic head in FIG. 4.

FIG. 6 is a perspective view showing a waveguide and a near-field lightgenerator plate in the thermally assisted magnetic head in FIG. 3.

FIG. 7 is an enlarged view of the near-field light generator plate inFIG. 6, wherein (a) is a plan view from the medium-facing surface and(b) is a horizontal sectional view of (a).

FIG. 8 is a schematic perspective view showing a configuration of alaser diode.

FIG. 9 is perspective views showing a production method of the waveguideand the near-field light generator plate in order of (A)-(D).

FIG. 10 is perspective views, subsequent to FIG. 9, showing theproduction method of the waveguide and the near-field light generatorplate in order of (A)-(C).

FIG. 11 is perspective views showing a production method of thethermally assisted magnetic head in order of (A) and (B).

FIG. 12 is a horizontal sectional view showing another form of thenear-field light generator plate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments for carrying out the present invention will be describedbelow in detail with reference to the accompanying drawings. In each ofthe drawings, the same elements will be denoted by the same referencenumerals. It is also noted that the dimensional ratios in and betweenthe constituent elements in the drawings are arbitrary, for easierunderstanding of the drawings.

FIG. 1 is a perspective view schematically showing a configuration of amajor part in an embodiment of the hard disk drive and HGA (head gimbalassembly) according to the present invention. FIG. 2 is an enlargedperspective view of a part near a thermally assisted magnetic head 21 inFIG. 1. In the perspective view of the HGA, the side of the HGA facing asurface of a magnetic disk is illustrated up.

(Hard Disk Drive)

In (A) of FIG. 1, the hard disk drive 1 has magnetic disks (recordingmedium) 10 consisting of a plurality of magnetic recording media torotate around a rotation shaft of spindle motor 11, an assembly carriagedevice 12 for positioning each thermally assisted magnetic head 21 on atrack, and a recording, reproduction, and emission control circuit(control circuit) 13 for controlling writing and reading operations ofeach thermally assisted magnetic head 21 and for controlling a laserdiode as a light source for emitting laser light for thermally assistedmagnetic recording, which will be detailed later.

The assembly carriage device 12 is provided with a plurality of drivearms 14. These drive arms 14 are angularly rockable around a pivotbearing shaft 16 by voice coil motor (VCM) 15, and are stacked in thedirection along this shaft 16. An HGA 17 is attached to the distal endof each drive arm 14. Each HGA 17 is provided with a thermally assistedmagnetic head 21 so that it faces the surface of each magnetic disk 10.The surface of the magnetic head 21 facing the surface of the magneticdisk 10 is a medium-facing surface S (which is also called an airbearing surface) of the thermally assisted magnetic head 21. The numberof each of magnetic disks 10, drive arms 14, HGAs 17, and thermallyassisted magnetic heads 21 may be one.

(HGA)

The HGA 17 is constructed, as shown in (B) of FIG. 1, by fixing thethermally assisted magnetic head 21 to a distal end of suspension 20 andelectrically connecting one end of wiring member 203 to terminalelectrodes of the thermally assisted magnetic head 21. The suspension 20is composed mainly of a load beam 200, a flexure 201 with elasticityfixed and supported on this load beam 200, a tongue portion 204 formedin a plate spring shape at the tip of the flexure, a base plate 202disposed on the base part of the load beam 200, and a wiring member 203disposed on the flexure 201 and consisting of a lead conductor andconnection pads electrically connected to the both ends of the leadconductor.

The wiring member, as shown in FIG. 2, has a pair of electrode pads 237,237 for recording signal, a pair of electrode pads 238, 238 for readoutsignal, and a pair of electrode pads 247, 248 for driving of the lightsource.

It is obvious that the structure of the suspension in the HGA 17 of thepresent invention is not limited to the above-described structure. An ICchip for driving of the head may be mounted midway in the suspension 20,though not shown.

(Thermally Assisted Magnetic Head)

As shown in FIGS. 2 to 4, the thermally assisted magnetic head 21 has aconfiguration in which a slider 22, and a light source unit 23 having alight source support substrate 230 and a laser diode 40 as a lightsource for thermally assisted magnetic recording are bonded and fixed toeach other so that a back surface 2201 of a slider substrate 220 is incontact with a bond surface 2300 of the light source support substrate230. The back surface 2201 of the slider substrate 220 herein is asurface opposite to the medium-facing surface S of the slider 22. Abottom surface 2301 of the light source support substrate 230 is bondedto the tongue portion 204 of the flexure 201, for example, with anadhesive such as epoxy resin.

(Slider)

The slider 22 has a slider substrate 220, and a magnetic head portion 32for performing writing and reading of data signal.

The slider substrate 220 is of a plate shape and has the medium-facingsurface S processed so as to achieve an appropriate levitation amount.The slider substrate 220 is made of electrically conductive AlTiC(Al₂O₃—TiC) or the like.

The magnetic head portion 32 is formed on an integration surface 2202which is a side surface approximately perpendicular to the medium-facingsurface S of the slider substrate 220. The magnetic head portion 32 hasan MR effect element (magnetic detecting element) 33 as a magneticdetecting element for detecting magnetic information, an electromagneticcoil element (magnetic recording element) 34 as a perpendicular (or,possibly, longitudinal) magnetic recording element for writing magneticinformation by generation of a magnetic field, a waveguide 35 as aplanar waveguide provided through between the MR effect element 33 andthe electromagnetic coil element 34, a near-field light generator plate36 for generating near-field light for heating a recording layer portionof a magnetic disk, an insulating layer 38 formed on the integrationsurface 2202 so as to cover these MR effect element 33, electromagneticcoil element 34, waveguide 35, and near-field light generator plate 36,a pair of electrode pads 371, 371 for signal terminals exposed from thelayer surface of the insulating layer 38 and connected to the MR effectelement 33, a pair of electrode pads 373, 373 for signal terminalsconnected to the electromagnetic coil element 34, and an electrode pad375 for ground electrically connected to the slider substrate 220. TheMR effect element 33, electromagnetic coil element 34, and near-fieldlight generator plate 36 are exposed in the medium-facing surface S.Each of the elements will be described below in detail.

FIG. 4 is a sectional view of the part near the magnetic head portion ofthe thermally assisted magnetic head 21. As shown in FIG. 4, the MReffect element 33 includes an MR laminate 332, and a lower shield layer330 and an upper shield layer 334 located at respective positions onboth sides of this MR laminate 332. The lower shield layer 330 and theupper shield layer 334 can be made, for example, of a magnetic materialof NiFe, CoFeNi, CoFe, FeN, FeZrN, or the like and in the thickness ofabout 0.5-3 μm by a pattern plating method including a frame platingmethod, or the like. The upper and lower shield layers 334 and 330prevent the MR laminate 332 from being affected by an external magneticfield serving as noise.

The M laminate 332 includes a magneto-resistance effect film such as anin-plane conduction type (CIP (Current In Plane)) Giant MagnetoResistance (GMR) multilayer film, a perpendicular conduction type (CPP(Current Perpendicular to Plane)) GMR multilayer film, or a TunnelMagneto Resistance (TMR) multilayer film, and is sensitive to a signalmagnetic field from the magnetic disk with very high sensitivity.

For example, when the MR laminate 332 includes a TMR effect multilayerfilm, it has a structure in which the following layers are stacked inorder: an antiferromagnetic layer made of IrMn, PtMn, NiMn, RuRhMn, orthe like and in the thickness of about 5-15 nm; a magnetization fixedlayer comprised, for example, of CoFe or the like as a ferromagneticmaterial, or two layers of CoFe or the like with a nonmagnetic metallayer of Ru or the like in between, and having the magnetizationdirection fixed by the antiferromagnetic layer; a tunnel barrier layerof a nonmagnetic dielectric material made, for example, by oxidizing ametal film of Al, AlCu, or the like about 0.5-1 nm thick by oxygenintroduced into a vacuum chamber, or by native oxidation; and amagnetization free layer comprised, for example, of two layered films ofCoFe or the like about 1 nm thick as a ferromagnetic material and NiFeor the like about 3-4 nm thick, and effecting tunnel exchange couplingthrough the tunnel barrier layer with the magnetization fixed layer.

An interelement shield layer 148 made of the same material as the lowershield layer 330 is formed between the MR effect element 33 and thewaveguide 35. The interelement shield layer 148 performs a function ofshielding the MR effect element 33 from a magnetic field generated bythe electromagnetic coil element 34 and preventing external noise duringreadout. A bucking coil portion may also be further formed between theinterelement shield layer 148 and the waveguide 35. The bucking coilportion generates a magnetic flux to cancel a magnetic flux loopgenerated by the electromagnetic coil element 34 and passing via theupper and lower electrode layers of the MR effect element 33, andthereby suppresses the Wide Area Track Erasure (WATE) phenomenon beingan unwanted writing or erasing operation on the magnetic disk.

The insulating layer 38 made of alumina or the like is formed betweenthe shield layers 330, 334 on the opposite side to the medium-facingsurface S of the MR laminate 332, on the opposite side to themedium-facing surface S of the shield layers 330, 334, 148, between thelower shield layer 330 and the slider substrate 220, and between theinterelement shield layer 148 and the waveguide 35.

When the MR laminate 332 includes a CIP-GMR multilayer film, upper andlower shield gap layers for insulation of alumina or the like areprovided between each of the upper and lower shield layers 334 and 330,and the MR laminate 332. Furthermore, an MR lead conductor layer forsupplying a sense current to the MR laminate 332 to extract reproductionoutput is formed though not shown. On the other hand, when the MRlaminate 332 includes a CPP-GMR multilayer film or a TMR multilayerfilm, the upper and lower shield layers 334 and 330 also function asupper and lower electrode layers, respectively. In this case, the upperand lower shield gap layers and MR lead conductor layer are unnecessaryand omitted.

A hard bias layer of a ferromagnetic material such as CoTa, CoCrPt, orCoPt, for applying a vertical bias magnetic field for stabilization ofmagnetic domains, is formed on both sides in the track width directionof the MR laminate 332, though not shown.

The electromagnetic coil element 34 is preferably one for perpendicularmagnetic recording and, as shown in FIG. 4, has a main magnetic polelayer 340, a gap layer 341 a, a coil insulating layer 341 b, a coillayer 342, and an auxiliary magnetic pole layer 344 as exposed in themedium-facing surface S.

The main magnetic pole layer 340 is a magnetic guide for guiding amagnetic flux induced by the coil layer 342, up to the recording layerof the magnetic disk (medium) as a target of writing, while convergingthe magnetic flux. The end of the main magnetic pole layer 340 on themedium-facing surface S side preferably has a width in the track widthdirection (depth direction in FIG. 4) and a thickness in the stackdirection (horizontal direction in FIG. 4) smaller than those of theother portions. This results in permitting the main magnetic pole layerto generate a fine and strong writing magnetic field adapted for highrecording density. Specifically, for example, as shown in FIG. 5 whichis a view of the magnetic head portion from the medium-facing surface Sside, the tip of the main magnetic pole layer 340 on the medium-facingsurface S side is preferably tapered in a shape of an inverted trapezoidwhose length of the side on the leading side or slider substrate 220side is shorter than the length of the side on the trailing side.Namely, the end face of the main magnetic pole layer 340 on themedium-facing surface side is provided with a bevel angle θ, in order toavoid unwanted writing or the like on an adjacent track by influence ofa skew angle made by actuation with a rotary actuator. The magnitude ofthe bevel angle θ is, for example, approximately 15°. In practice, thewriting magnetic field is generated mainly near the longer side on thetrailing side and in the case of the magnetic dominant recording, thelength of this longer side determines the width of the writing track.

Here the main magnetic pole layer 340 is preferably made, for example,in the total thickness of about 0.01 to about 0.5 μm at the end portionon the medium-facing surface S side and in the total thickness of about0.5 to about 3.0 μm at the portions other than this end portion and, forexample, of an alloy of two or three out of Ni, Fe, and Co by frameplating, sputtering, or the like, or an alloy containing the foregoingelements as main ingredients and doped with a predetermined element. Thetrack width can be, for example, 100 nm.

As shown in FIG. 4, the end portion of the auxiliary magnetic pole layer344 on the medium-facing surface S side forms a trailing shield portionwider in a layer section than the other portion of the auxiliarymagnetic pole layer 344. The auxiliary magnetic pole layer 344 isopposed through the gap layer 341 a and coil insulating layer 341 b madeof an insulating material such as alumina, to the end of the mainmagnetic pole layer 340 on the medium-facing surface S side. When theauxiliary magnetic pole layer 344 of this configuration is provided, themagnetic field gradient becomes steeper between the auxiliary magneticpole layer 344 and the main magnetic pole layer 340 near themedium-facing surface S. This results in decreasing jitter of signaloutput and permitting decrease in the error rate during readout.

The auxiliary magnetic pole layer 344 is made, for example, in thethickness of about 0.5 to about 5 μm and, for example, of an alloy oftwo or three out of Ni, Fe, and Co by frame plating, sputtering, or thelike, or an alloy containing these as principal ingredients and dopedwith a predetermined element.

The gap layer 341 a separates the coil layer 342 from the main magneticpole layer 340 and is made, for example, in the thickness of about 0.01to about 0.5 μm and, for example, of Al₂O₃ or DLC or the like bysputtering, CVD, or the like.

The coil layer 342 is made, for example, in the thickness of about 0.5to about 3 μm and, for example, of Cu or the like by frame plating orthe like. The rear end of the main magnetic pole layer 340 is coupledwith the portion of the auxiliary magnetic pole layer 344 apart from themedium-facing surface S and the coil layer 342 is formed so as tosurround this coupling portion. The coil layer 342 is one layer in FIG.4 and others, but may be two or more layers, or a helical coil.

The coil insulating layer 341 b separates the coil layer 342 from theauxiliary magnetic pole layer 344 and is made, for example, in thethickness of about 0.1 to about 5 μm and of an electric insulatingmaterial such as thermally cured alumina or resist layer or the like.

The waveguide 35 is located between the MR effect element 33 and theelectromagnetic coil element 34, extends in parallel with theintegration surface 2202, extends from the medium-facing surface S ofthe magnetic head portion 32 to the surface 32 a opposite to themedium-facing surface of the magnetic head portion 32, and is of arectangular plate shape, as shown in FIG. 6. The waveguide 35 has twoside faces 351 a, 351 b opposed in the track width direction, and twoupper face 352 a and lower face 352 b parallel to the integrationsurface 2202, all of which are formed perpendicularly to themedium-facing surface S, and the waveguide 35 also has an exit face 353forming the medium-facing surface S, and an entrance face (end face) 354opposite to the exit face 353. The upper face 352 a, the lower face 352b, and the two side faces 351 a, 351 b of the waveguide 35 are incontact with the insulating layer 38 having the refractive index smallerthan that of the waveguide 35 and functioning as a cladding for thewaveguide 35.

This waveguide 35 is able to guide light incident through the entranceface 354, to the exit face 353 as the end face on the medium-facingsurface S side, while reflecting the light on the two side faces 351 a,351 b, the upper face 352 a, and the lower face 352 b. The width W35 ofthe waveguide 35 in the track width direction in FIG. 6 can be, forexample, 1-200 μm, the thickness T35, for example, 2-10 μm, and theheight H35 10-300 μm.

The waveguide 35 is made, for example, by sputtering or the like, from adielectric material which has the refractive index n higher than that ofthe material making the insulating layer 38, everywhere. For example, ina case where the insulating layer 38 is made of SiO₂ (n=1.5), thewaveguide 35 may be made of Al₂O₃ (n=1.63). Furthermore, in a case wherethe insulating layer 38 is made of Al₂O₃ (n=1.63), the waveguide 35 maybe made of Ta₂O₅ (n=2.16), Nb₂O₅ (n=2.33), TiO (n=2.3-2.55), or TiO₂(n=2.3-2.55). When the waveguide 35 is made of one of such materials,the total reflection condition is met at the interface, in addition tothe good optical characteristics of the material itself, so as todecrease the propagation loss of laser light and increase the efficiencyof generation of near-field light.

The near-field light generator plate 36, as shown in FIGS. 2, and 4 to7, is a platelike member disposed nearly in the center of the exit face353 of the waveguide 35. As shown in FIGS. 4 and 6, the near-field lightgenerator plate 36 is buried in the exit face 353 of the waveguide 35 sothat the principal face thereof is exposed in the medium-facing surfaceS to face the medium. As shown in FIG. 5, the near-field light generatorplate 36 is of a triangular shape when viewed from the medium-facingsurface S, and is made of an electroconductive material. Theelectroconductive material can be one selected from metals and alloyssuch as Au, and others.

A base 36 d of the triangle is arranged in parallel with the integrationsurface 2202 of the slider substrate 220 or in parallel with the trackwidth direction, and a pointed cusp portion 36 c opposed to the base 36d is arranged on the main magnetic pole layer 340 side of theelectromagnetic coil element 34 with respect to the base 36 d;specifically, the cusp portion 36 c is arranged opposite to the leadingedge of the main magnetic pole layer 340. A preferred form of thenear-field light generator plate 36 is an isosceles triangle whose twobase angles at the two ends of the base 36 d are equal to each other.

In the near-field light generator plate 36, as shown in FIGS. 5 and 7,an electroconductive layer 36 a (other portion) farther from the mainmagnetic pole 340 and an electroconductive layer 36 b (one portion)closer to the main magnetic pole 340 are made of their respectiveelectroconductive materials different from each other. The “materialsdifferent from each other” means that their compositions are different,and the different compositions enable the electroconductive layer 36 a(other portion) farther from the main magnetic pole 340 and theelectroconductive layer 36 b (one portion) closer to the main magneticpole 340 to have different surface removal speeds such as polishingspeeds or etching speeds. Specifically, each of the electroconductivelayers 36 a, 36 b of the near-field light generator plate 36 ispreferably made of a metal or an alloy of two or more metals selectedfrom the group consisting of Pd, Pt, Rh, Ir, Ru, Au, Ag, Cu, and Al.

The electroconductive layer 36 b closer to the main magnetic pole 340 inthe near-field light generator plate preferably includes a pointed cuspportion 36 c as a place for selectively generating the near-field lightand, particularly, more preferably has only one cusp portion. In FIG. 5,the radius of curvature at the tip of the cusp portion 36 c ispreferably 5-100 nm.

The height H36 of the triangle is sufficiently smaller than thewavelength of incident laser light and is preferably 20-400 nm. Thewidth W36 of the base 36 d is sufficiently smaller than the wavelengthof incident laser light and is preferably 20-400 nm.

In the present embodiment, particularly as shown in FIG. 7, amedium-facing surface 36 bS of the electroconductive layer 36 b closerto the main magnetic pole 340 is projected more toward the medium 10than a medium-facing surface 36 aS of the electroconductive layer 36 afarther from the main magnetic pole 340. For example, a thickness T36 bof the electroconductive layer 36 b closer to the main magnetic pole 340can be, for example, 10-100 nm and a level difference D between themedium-facing surface 36 aS and the medium-facing surface 36 bS can be,for example, 5-50 nm.

When the near-field light generator plate 36 is disposed on the exitface 353 of the waveguide 35, the electric field is concentrated nearthe cusp portion 36 c in the electroconductive layer 36 b of thenear-field light generator plate 36 and the near-field light isselectively generated from near the cusp portion 36 c toward the medium.This will be detailed later.

In this slider 22, as shown in FIG. 2, the electrode pads 371, 371 areelectrically connected through bonding wires to the respective electrodepads 237, 237 of the flexure 201, and the electrode pads 373, 373 areconnected through bonding wires to the respective electrode pads 238,238 of the flexure 201; this configuration allows each of theelectromagnetic coil element and the MR effect element to be driven. Theelectrode pad 375 electrically connected through a via hole 375 a inFIG. 4 to the slider substrate 220 is connected through a bonding wireto the electrode pad 247 of the flexure 201, as shown in FIG. 2, wherebya potential of the slider substrate 220 can be controlled, for example,to the ground potential by the electrode pad 247.

(Light Source Unit)

The components of the light source unit 23 in the thermally assistedmagnetic head 21 will be described below.

As shown in FIGS. 2 to 4, the light source unit 23 mainly has a lightsource support substrate 230 and a laser diode (light source) 40 whosecontour is platelike.

The light source support substrate 230 is a substrate of AlTiC(Al₂O₃—TiC) or the like and has the bond surface 2300 bonded to the backsurface 2201 of the slider substrate 220. As shown in FIG. 4, a heatinsulation layer 230 a of alumina or the like is formed on the bondsurface 2300. An insulating layer 41 of an insulating material such asalumina is disposed on an element forming surface 2302 being one sidesurface when the bond surface 2300 is regarded as a bottom surface. Theelectrode pads 47, 48 are formed on this insulating layer 41, and thelaser diode 40 is fixed on the electrode pad 47.

More specifically, as shown in FIGS. 2 and 3, the electrode pads 47, 48are formed for driving of laser, on a surface 411 intersecting with thefront surface of the insulating layer 41 and with the medium-facingsurface S and, in other words, they are formed on the surface 411parallel to the integration surface 2202 of the slider substrate 220.The electrode pad 47, as shown in FIG. 4, is electrically connectedthrough a via hole 47 a provided in the insulating layer 41, to thelight source support substrate 230. The electrode pad 47 also functionsas a heat sink for leading heat during driving of the laser diode 40through the via hole 47 a to the light source support substrate 230side.

The electrode pad 47, as shown in FIG. 2, is formed so as to extend inthe track width direction in the central region of the surface 411 ofthe insulating layer 41. On the other hand, the electrode pad 48 isformed at a position separate in the track width direction from theelectrode pad 47. Each of the electrode pads 47, 48 further extendstoward the flexure 201 side, for connection with the flexure 201 bysolder reflow.

The electrode pads 47, 48 are electrically connected to the electrodepads 247, 248 of the flexure 201, respectively, by reflow soldering,whereby the light source can be driven. Since the electrode pad 47 iselectrically connected to the light source support substrate 230 asdescribed above, the potential of the light source support substrate 230can be controlled, for example, to the ground potential by the electrodepad 247.

The electrode pads 47, 48 can be comprised, for example, of layers ofAu, Cu, or the like made in the thickness of about 1-3 μm and by vacuumevaporation, sputtering, or the like, which are formed, for example,through a ground layer of Ta, Ti, or the like about 10 nm thick.

The laser diode 40 is electrically connected onto the electrode pad 47by a solder layer 42 (cf. FIG. 4) of an electrically conductive soldermaterial such as Au—Sn. At this time, the laser diode 40 is locatedrelative to the electrode pad 47 so as to cover only a part of theelectrode pad 47.

As shown in FIG. 8, the laser diode 40 may have the same structure asthe one normally used for an optical disk storage, and, for example, hasa structure in which the following layers are stacked in order: ann-electrode 40 a; an n-GaAs substrate 40 b; an n-InGaAlP cladding layer40 c; a first InGaAlP guide layer 40 d; an active layer 40 e consistingof multiple quantum wells (InGaP/InGaAlP) or the like; a second InGaAlPguide layer 40 f; a p-InGaAlP cladding layer 40 g; an *n-GaAs currentblocking layer 40 h; a p-GaAs contact layer 40 i; a p-electrode 40 j.Reflecting films 50 and 51 of SiO₂, Al₂O₃, or the like for excitingoscillation by total reflection are deposited before and after cleavagefaces of the multilayer structure, and an aperture is provided at theposition of the active layer 40 e in one reflecting film 50, at anoutput end 400 for emission of laser light. The laser diode 40 of thisconfiguration emits laser light from the output end 400 when a voltageis applied thereto in the film thickness direction.

The wavelength λ_(L) of the emitted laser light is, for example,approximately 600-650 nm. It should be, however, noted that there is anappropriate excitation wavelength according to the metal material of thenear-field light generator plate 36 (FIG. 2). For example, in a casewhere either of Au and an alloy thereof is used for the near-field lightgenerator plate 36 and where the height H36 of the triangle is about 100nm, the wavelength λ_(L) of the laser light is preferably near 600 nm.

The size of the laser diode 40 is, for example, the width (W40) of200-350 μm, the length (depth L40) of 250-600 μm, and the thickness(T40) of about 60-200 μm, as described above. The width W40 of the laserdiode 40 can be decreased, for example, to about 100 μm, while theminimum thereof is a spacing between opposed ends of the currentblocking layer 40 h. However, the length of the laser diode 40 is thequantity associated with the electric current density and thus cannot bedecreased so much. In either case, the laser diode 40 is preferablydimensioned in a sufficient size, in consideration of handling duringmounting.

A power supply in the hard disk drive can be used for driving of thislaser diode 40. In practice, the hard disk drive is usually equipped,for example, with the power supply of about 2 V, which is a sufficientvoltage for the lasing operation. The power consumption of the laserdiode 40 is also, for example, approximately several ten mW, which thepower supply in the hard disk drive can fully provide.

In FIG. 4, the n-electrode 40 a of the laser diode 40 is fixed to theelectrode pad 47 by the solder layer 42 such as AuSn. The laser diode 40is fixed to the light source support substrate 230 so that the outputend 400 of the laser diode 40 is directed downward in FIG. 4, i.e., sothat the output end 400 becomes parallel to the bond surface 2300;whereby the output end 400 can face the entrance face 354 of thewaveguide 35 of the slider 22. In practical fixing of the laser diode40, for example, an evaporated film of AuSn alloy is deposited in thethickness of about 0.7-1 μm on the surface of the electrode pad 47, thelaser diode 40 is mounted thereon, and thereafter it is heated to befixed, to about 200-300° C. by a hot plate or the like under a hot airblower. As shown in FIGS. 2 and 8, the electrode pad 48 is electricallyconnected through a bonding wire to the p-electrode 40 j of the laserdiode 40. The electrode connected to the electrode pad 47 may also bethe p-electrode 40 j, instead of the n-electrode 40 a, and in this case,the n-electrode 40 a is connected through a bonding wire to theelectrode pad 48.

In the case of soldering with the aforementioned AuSn alloy, the lightsource unit is heated, for example, to the high temperature of about300° C., but according to the present embodiment, this light source unit23 is produced separately from the slider 22; therefore, the magnetichead portion in the slider is prevented from being adversely affected bythis high temperature.

The back surface 2201 of the aforementioned slider 22 and the bondsurface 2300 of the light source unit 23 are bonded, for example, withan adhesive layer 44 such as a UV cure type adhesive, as shown in FIG.4, and the output end 400 of the laser diode 40 is arranged opposite tothe entrance face 354 of the waveguide 35.

The configurations of the laser diode 40 and the electrode pads do notalways have to be limited to those in the above-described embodiment, ofcourse, and, for example, the laser diode 40 may be one of anotherconfiguration using other semiconductor materials, such as GaAlAs typematerials. Furthermore, it is also possible to use any other brazingmaterial, for the soldering between the laser diode 40 and theelectrodes. Yet furthermore, the laser diode 40 may be formed directlyon the unit substrate by epitaxially growing the semiconductormaterials.

The sizes of the slider 22 and the light source unit 23 are arbitrary,but the slider 22 may be, for example, a so-called femtoslider havingthe width of 700 μm in the track width direction×length (depth) of 850μm×thickness of 230 μm. In this case, the light source unit 23 can havethe width and length approximately equal to them. In fact, for example,the typical size of the ordinary laser diode is approximately the widthof 250 μm×length (depth) of 350 μm×thickness of 65 μm, and the laserdiode 40 of this size can be adequately mounted, for example, on theside surface of the light source support substrate 230 of this size. Itis also possible to make a groove in the bottom surface of the lightsource support substrate 230 and locate the laser diode 40 in thisgroove.

The spot of the far field pattern of the laser light reaching theentrance face 354 of the waveguide 35 can be made in the size in thetrack width direction, for example, of about 0.5-1.0 μm and the sizeperpendicular to the foregoing size, for example, of about 1-5 μm. Incorrespondence thereto, the thickness T35 of the waveguide 35 receivingthis laser light is preferably, for example, about 2-10 μm so as to belarger than the spot and the width (W35) in the track width direction ofthe waveguide 35 is preferably, for example, about 1-200 μm.

The heat insulation layer 230 a may be formed on the back surface 2201of the slider substrate 220, and the present invention can also becarried out without the heat insulation layer.

(Production Method)

Subsequently, a method of producing the thermally assisted magnetic headdescribed above will be described below briefly.

First, the slider 22 is produced. Specifically (with reference to FIG.4), the slider substrate 220 is prepared, the MR effect element 33 andinterelement shield layer 148 are formed by well-known methods, and apart (38 a hereinafter) of the insulating layer 38 of Al₂O₃ or the likeis further formed as a ground layer.

Subsequently, the waveguide 35 and near-field light generator plate 36are formed. This process will be described in detail with reference toFIGS. 9 and 10. FIGS. 9 and 10 are perspective views to illustrate anembodiment of the method of forming the waveguide 35 and the near-fieldlight generator plate 36.

In the first step, as shown in (A) of FIG. 9, a dielectric film 35 a ofTa₂O₅ or the like with the refractive index higher than that of theinsulating layer 38 a, which will be a part of the waveguide 35, isfirst deposited on the insulating layer 38 a of Al₂O₃ or the like, andthe electroconductive layer 36 a and the electroconductive layer 36 bare deposited thereon, and a resist pattern 1002 depressed for liftoffin the bottom part is formed thereon. The electroconductive layers 36 aand 36 b are made of their respective electroconductive materialsdifferent from each other.

In the next step, as shown in (B) of FIG. 9, unnecessary portions of theelectroconductive layers 36 a and 36 b are removed except immediatelybelow the resist pattern 1002 by ion milling or the like, therebyforming a laminate for near-field light generator plate 36 which has atrapezoid sectional shape wider in the bottom and which consists of theelectroconductive layers 36 a and 36 b, on the dielectric film 35 a.

In the subsequent step, as shown in (C) of FIG. 9, the resist pattern1002 is removed, and then a part of each slope is removed from the twoslope sides of the laminate for near-field light generator plate 36 ofthe trapezoid shape by ion milling or the like, to form the laminate fornear-field light generator plate 36 in a triangular sectional shape.

Subsequently, as shown in (D) of FIG. 9, a dielectric film 35 b of thesame material as the dielectric film 35 a is deposited on the dielectricfilm 35 a so as to cover the laminate for near-field light generatorplate 36, a resist pattern 1003 for formation of the end face of thelaminate for near-field light generator plate 36 is laid on the sidewhere the medium-facing surface will be formed, the laminate fornear-field light generator plate 36, dielectric film 35 c and thedielectric film 35 b are removed by ion milling or the like, from theside opposite to the side where the medium-facing surface will beformed, as shown in (A) of FIG. 10, and thereafter a dielectric film 35c of the same material as the dielectric film 35 b is deposited on theremoved portion.

Furthermore, as shown in (B) of FIG. 10, a dielectric film 35 d of thesame material as the dielectric film 35 b is further deposited on thedielectric films 35 b, 35 c, and the dielectric films 35 a, 35 b, 35 c,35 d are patterned so as to achieve a predetermined width, therebyalmost completing the waveguide 35.

Thereafter, as shown in (C) of FIG. 10, an insulating layer 38 b of thesame material as the insulating layer 38 a is further formed so as tocover the waveguide 35, thereby completing the insulating layer 38 as acladding layer. Then the surface is removed by a predetermined distancefrom the side where the laminate for near-field light generator plate 36is exposed, to form the near-field light generator plate 36 of thepredetermined thickness, and the medium-facing surface S.

This surface removing method is not particularly limited and is, forexample, a step of removing the surface on the medium-facing surfaceside by a predetermined thickness by any one of various methods, e.g.,lapping (polishing) methods such as mechanical polishing and chemicalmechanical polishing (CMP), etching methods such as ion beam etching,plasma etching, reactive ion etching, and chemical etching, andarbitrary combinations of these. Since in the near-field light generatorplate 36 the electroconductive layers 36 a and 36 b are made of theirrespective electroconductive materials different from each other, thereis the difference between their surface removal speeds (polishingspeeds, etching speeds, or the like), whereby the fine level differenceD shown in FIG. 7 can be readily made between the electroconductivelayer 36 a and the electroconductive layer 36 b.

The combination of the electroconductive materials of theelectroconductive layers 36 a and 36 b is preliminarily determined to bea combination realizing the mutually different surface removal speeds inthe surface removing method, according to the method of removing thesurface of the medium-facing surface. Namely, a layer of anelectroconductive material with a relatively low surface removal speedis located in the portion expected to project toward the medium and alayer of an electroconductive material with a relatively high surface.removal speed is located in the portion expected not to project towardthe medium. Specifically, for example, in the lapping case,electroconductive materials with mutually different hardnesses are used;and in the etching case electroconductive materials with mutuallydifferent etching speeds are used.

A preferred combination of compositions of electroconductive materialsis such that the surface removal speed of the electroconductive layer 36a farther from the main magnetic pole 340 of the near-field lightgenerator plate 36 is larger than the surface removal speed of theelectroconductive layer 36 b closer to the main magnetic pole 340. Forexample, from the viewpoint of making the difference between polishingspeeds or hardnesses, a preferred combination is such that theelectroconductive layer 36 a farther from the main magnetic pole 340 inthe near-field light generator plate 36 is made of Au and theelectroconductive layer 36 b closer to the main magnetic pole 340 ismade of AuCu.

The above steps can form the waveguide 35 with the near-field lightgenerator plate 36.

After that, the electromagnetic coil element 34 is formed by thewell-known method as shown in FIG. 4, and then the insulating layer 38of alumina or the like is formed. Furthermore, the electrode pads 371and others for connection are formed and thereafter lapping of the airbearing surface and the back surface thereof is performed to completethe slider 22. After this step, tests of the electromagnetic coilelement 34 and the MR effect element 33 of slider 22 are conducted foreach slider, to select a nondefective product.

Subsequently, the light source unit 23 is produced. In the first step,as shown in FIG. 4, the light source support substrate 230 of AlTiC orthe like is prepared, the heat insulation layer 230 a, insulating layer41, and electrode pads 47, 48 are formed on the surfaces of thesubstrate by well-known methods, the laser diode 40 is fixed on theelectrode pad 47 by an electrically conductive solder material such asAuSn, and thereafter the substrate is shaped into a predetermined sizeby separation by cutting of the substrate, or the like. This completesthe light source unit 23. The light source unit obtained in this manneris also subjected to characteristic evaluation of the laser diode,particularly, observation of a profile of drive current by ahigh-temperature continuous conduction test, to select one considered tohave a sufficiently long life.

After that, as shown in (A) of FIG. 11, a UV cure type adhesive 44 a isapplied onto either or both of the bond surface 2300 of the light sourceunit 23 as a nondefective unit and the back surface 2201 of the slider22 as a nondefective unit. The UV cure type adhesive can be a UV curetype epoxy resin, a UV cure type acrylic resin, or the like. Theadhesion between the light source unit 23 and the slider 22 can also beimplemented with an adhesive except for the UV cure type adhesive, e.g.,with a solder layer of AuSn or the like which was used for adhesionbetween the laser diode 40 and the electrode pad 47.

Then, as shown in (B) of FIG. 11, the bond surface 2300 of the lightsource unit 23 and the back surface 2201 of the slider 22 are laid oneach other, and then the laser diode 40 is activated with application ofa voltage between the electrode pads 47, 48, and a photodetector DT isopposed to the exit face 353 of the waveguide 35. The light source unit23 and the slider 22 are relatively moved in directions of arrows in (B)of FIG. 11 to find out a position where the output from thephotodetector DT becomes maximum. At that position, UV light is appliedfrom the outside onto the UV cure type adhesive to cure the UV cure typeadhesive 44 a, which can bond the light source unit 23 and the slider 22to each other in a state in which the optical axis of the laser diode isaligned with the optical axis of the waveguide 35.

(Action)

Subsequently, the action of the thermally assisted magnetic head 21according to the present embodiment will be described below.

During a writing or reading operation, the thermally assisted magnetichead 21 hydromechanically floats up by a predetermined levitation amountabove the surface of the rotating magnetic disk (medium) 10. On thisoccasion, the ends on the medium-facing surface S side of the MR effectelement 33 and the electromagnetic coil element 34 are opposed through asmall spacing to the magnetic disk 10, thereby implementing readout bysensing of a data signal magnetic field and writing by application of adata signal magnetic field.

On the occasion of writing of a data signal, the laser light havingpropagated from the light source unit 23 through the waveguide 35reaches the near-field light generator plate 36, whereupon thenear-field light generator plate 36 generates the near-field light. Thisnear-field light enables execution of thermally assisted magneticrecording as described below.

Here the near-field light generally has the maximum intensity at theborder of the near-field light generator plate 36 when viewed from themedium-facing surface S, though it depends upon the wavelength of theincident laser light and the shape of the waveguide 35. Particularly,the present embodiment is arranged as follows in FIG. 4: the stackdirection of the laser diode 40 is the horizontal direction in FIG. 4;the electric field vector of the light arriving at the near-field lightgenerator plate 36 is the horizontal direction in FIG. 4, i.e., thevertical direction in FIG. 5. Furthermore, since in the presentembodiment the electroconductive layer 36 b including the cusp portion36 c projected in the direction of the electric field vector isprojected more toward the medium than the electroconductive layer 36 aas shown in FIG. 7, radiation of the strongest near-field light occursnear the cusp portion 36 c of the electroconductive layer 36 b, wherebythe near-field light can be prevented from being radiated from the edgesand corners of the electroconductive layer 36 a. In the thermal assistaction to heat the recording layer portion of the magnetic disk withlight, the portion facing the neighborhood of this cusp portion 36 cbecomes a main heat-acting area.

Since the electric field intensity of this near-field light isimmeasurably stronger than that of the incident light, this very strongnear-field light rapidly heats the opposed local part of the surface ofthe magnetic disk. This reduces the coercivity of this local part to alevel allowing writing with the writing magnetic field, whereby writingwith the electromagnetic coil element 34 becomes feasible even with useof the magnetic disk of high coercivity for high-density recording. Thenear-field light penetrates, for example, to the depth of about 10-30 nmfrom the medium-facing surface S toward the surface of the magneticdisk. Therefore, under the present circumstances where the levitationamount is 10 nm or less, the near-field light can reach the recordinglayer part sufficiently. The width in the track width direction and thewidth in the medium-moving direction of the near-field light generatedin this manner are approximately equal to the aforementioned reach depthof the near-field light, and the electric field intensity of thisnear-field light exponentially decreases with increase in the distance;therefore, the near-field light can heat the recording layer part of themagnetic disk in an extremely localized area.

By adopting the thermally assisted magnetic recording as describedabove, it also becomes feasible to achieve, for example, the recordingdensity of 1 Tbits/in² order, by performing writing on the magnetic diskof high coercivity by means of the thin film magnetic head forperpendicular magnetic recording to record recording bits in anextremely fine size.

The present embodiment uses the light source unit 23, so that the laserlight propagating in the direction parallel to the layer surface of thewaveguide 35 can be made incident to the entrance face (end face) 354 ofthe waveguide 35 of the slider 22. Namely, the laser light ofappropriate size and direction can be surely supplied in the thermallyassisted magnetic head 21 having the configuration in which theintegration surface 2202 and the medium-facing surface S areperpendicular to each other. As a result, it is feasible to implementthe thermally assisted magnetic recording with high heating efficiencyof the recording layer of the magnetic disk.

Since in the present embodiment the magnetic head portion 32 is fixed tothe slider substrate 220 and the laser diode 40 as the light source isseparately fixed to the light source support substrate 230, thethermally assisted magnetic head 21 as a nondefective product can beproduced with a good yield by individually testing each of theelectromagnetic coil element 34 fixed to the slider substrate 220 andthe laser diode 40 fixed to the light source support substrate 230, andthereafter fixing the slider 22 as a nondefective unit and the lightsource unit 23 as a nondefective unit to each other.

Since the magnetic head portion 32 is disposed on the side surface ofthe slider substrate 220, the electromagnetic coil element 34, the MReffect element 33, and others of the magnetic head portion 32 can bereadily formed by the production methods of the conventional thin filmmagnetic heads.

Furthermore, since the laser diode 40 is located at the position apartfrom the medium-facing surface S and near the slider 22, it is feasibleto suppress the adverse effect of the heat generated from the laserdiode 40, on the electromagnetic coil element 34, the MR effect element33, etc., and the possibilities of contact or the like between the laserdiode 40 and the magnetic disk 10, to reduce the propagation loss oflight because of the dispensability of an optical fiber, a lens, amirror, etc., and to simplify the structure of the entire magneticrecording apparatus.

The arrangement method of the laser diode 40 is not limited to the abovedescription, but it is also possible to adopt an arrangement way whereinthe slider substrate 220 and the light source support substrate 230 areintegrally formed, or an arrangement way wherein an optical fiber or thelike is used to guide the light from the laser diode 40 to the waveguide35 and the near-field light generator plate 36. Furthermore, the presentinvention can also be carried out by arranging the waveguide 35 and thenear-field light generator plate 36 on the medium-facing surface of theslider substrate 220.

The electromagnetic coil element 34 may be one for longitudinal magneticrecording. In this case, a lower magnetic pole layer and an uppermagnetic pole layer are provided instead of the main magnetic pole layer340 and the auxiliary magnetic pole layer 344, and a writing gap layeris interposed between the ends on the medium-facing surface S side ofthe lower magnetic pole layer and the upper magnetic pole layer. Writingis implemented with a leakage magnetic field from the position of thiswriting gap layer.

The shape of the near-field light generator plate 36 is not limited tothe one described above, either, and the present invention can also becarried out, for example, by a trapezoid shape in which the tip of thecusp portion 36 c is somewhat flat, instead of the triangular shape. Thepresent invention can also be carried out by a so-called “bow tie type”structure in which a pair of sheets of a triangular shape or atrapezoidal shape are opposed to each other with their cusp portionsbeing spaced by a predetermined distance. In this “bow tie type”structure, a very strong electric field is concentrated in the centralregion thereof. In either case, the point is that the differentmaterials are used for the portion where the near-field light isexpected to be generated and for the other portion in the near-fieldlight generator plate and that the portion where the near-field light isexpected to be generated is projected more toward the medium than theother portion. For example, in the trapezoid case, the materials can beselected so that the cusp portion (upper base side) is projected moretoward the medium than the other portion (lower base side). In the caseof the bow tie structure in which a pair of plates are arranged, thematerials can be selected so that the cusp portions of the respectiveplates are projected more toward the medium than the other portions ofthe respective plates.

In the near-field light generator plate 36, the whole in the thicknessdirection perpendicular to the medium-facing surface S does not have tobe made from the same material but it is also possible to adopt, forexample as shown in FIG. 12, a configuration wherein the medium-facingsurface side is comprised of two electroconductive layers 36 a, 36 b ofrespective electroconductive materials different from each other andwherein the side other than the medium-facing surface is comprised ofone electroconductive layer 36 b. Namely, the point is that there aretwo electroconductive layers of mutually different electroconductivematerials in the medium-facing surface S. It is also possible to adopt aconfiguration wherein there are three or more electroconductive layersinstead of the two electroconductive layers.

The production method of the near-field light generator plate before thesurface removing step is not limited to the above-described one, either,and it is also possible to adopt, for example, a method of forming atrench for receiving the near-field light generator plate, in the endface of the waveguide by milling or the like from the medium-facingsurface side, and putting an electroconductive material in the trench bysputtering or the like.

It should be noted that the above-described embodiments all weredescribed as illustrative of the present invention but not restrictiveof the invention, and that the present invention can also be carried outin a variety of other modification and change forms. Therefore, thescope of the present invention should be defined by the scope of claimsand scope of equivalents thereof only.

1. A near-field light generator plate which is arranged so that aprincipal surface thereof faces a medium, and in which one portion andother portion in the principal surface are made of respectiveelectroconductive materials different from each other.
 2. The near-fieldlight generator plate according to claim 1, wherein each of theelectroconductive materials is a metal or an alloy of two or more metalsselected from a metal group consisting of Pd, Pt, Rh, Ir, Ru, Au, Ag,Cu, and Al.
 3. The near-field light generator plate according to claim1, wherein the electroconductive material of the one portion has ahigher hardness or a lower etching speed than the electroconductivematerial of the other portion.
 4. The near-field light generator plateaccording to claim 1, wherein the one portion is projected more towardthe medium than the other portion.
 5. The near-field light generatorplate according to claim 3, wherein, when viewed from a direction normalto the medium-facing surface, the one portion has a cusp portion.
 6. Thenear-field light generator plate according to claim 3, wherein the oneportion is made of AuCu and the other portion is made of Au.
 7. Athermally assisted magnetic head comprising: a magnetic pole forgenerating a magnetic field, which is exposed in a medium-facingsurface; a waveguide for receiving light from the outside and guidingthe light to the medium-facing surface; and the near-field lightgenerator plate as defined in claim 1, which is disposed on amedium-facing surface of the waveguide.
 8. A thermally assisted magnetichead comprising: a magnetic pole for generating a magnetic field, whichis exposed in a medium-facing surface; a waveguide for receiving lightfrom the outside and guiding the light to the medium-facing surface; andthe near-field light generator plate as defined in claim 3, which isdisposed on a medium-facing surface of the waveguide; wherein in themedium-facing surface, the one portion of the near-field light generatorplate is closer to the magnetic pole than the other portion thereof. 9.A head gimbal assembly comprising: the thermally assisted magnetic headas defined in claim 7; and a suspension supporting the thermallyassisted magnetic head.
 10. A hard disk drive comprising the head gimbalassembly as defined in claim 9; and a magnetic recording medium.